Radial lip seals are commonly used in journal boxes for sealing rotating shafts and in hinge joints for sealing oscillating pins and the like. The most common radial lip seals have a U-cup type of construction. In relatively clean environments, a little amount of inward radial load is required on the seal lip to seal in bearing lubricant. As the operating environment becomes dirtier and more severe, higher lip loads are required to ensure good sealability and to keep abrasive contaminants away from the bearings of such journal boxes or hinge joints. Garter springs have been frequently employed about such seal lips to increase the inward radial load on the lip so as to enhance its sealing ability. However, the amount of inward radial force that can be afforded by such garter spring devices is limited due to size constraints in view of the limited amount of space available for the seal and springs. Also in the typical U-cup seal, the seal lip is located at the distal end of one of the legs of the U-cup, providing an elastomeric hinge construction about which the lip moves. Such hinges do not respond rapidly at low temperatures. This low response rate can allow the seal lip to lift off of a pin that is shock loaded, for instance, so as to undergo a rapid radial deflection. Such lift off permits lubricant leakage and the entry of injurious contaminants.
Pin joints on the loader linkages of earthmoving vehicles present one of the most severe environments possible for seals. In such extremely severe applications, a very high inward radial force is desirable to prevent highly abrasive contaminants, such as mixtures of sand, dirt, and water, from not only entering the joint itself, but from becoming lodged under the seal lip, as abrasives under the lip will quickly grind a groove into the pin and/or quickly wear out the seal lip. Either of these results will lead to the entry of such contaminants into the joint and early joint failure. It has been found that the amount of radial force that can be provided by garter springs is insufficient to seal out such abrasives in the severe environments found in earthmoving applications.
The present invention is directed to overcoming the shortcomings of the prior attempts in radial lip seals at providing a sufficient amount of inward radial force on the seal lip to seal out abrasive contaminants in extremely severe applications, as well as providing better low temperature seal lip response.